Apparatus for cooling a stream of



Aug. 22, 1944.

M. H. OLSTAD ETAL APPARATUS FOR COOLING STREAMS OF FLUID Original FiledNov. 17, 1941 I INVENTOR mwzzoaam M 7 ivrromuzg.

- water necessary for the We Aug. 1944 Re. 22,533 f 22,53: ArrAnA'rUsron 000mm A s'raaAM or rwm 7 Martin a. Olstad, Bayside, one Allan E.Williams,

White Plains, N. 1., alsignors to Niagara Blower Company, New York, N.

York

Y.. a corporation oililew Original No. 2,296,946, dated September 29,1942,

Serial No. 419,412, November 17, 1941. Application for reissue October11, 1943, Serial No.

This invention relates to apparatus for cooling a stream of fluid andmore particularly is shown,

as an example of its use, as embodied and carried out in a heatexchanger for maintaining the desired temperature of quenching oil usedin tempering steel. However, the invention can be used in conjunctionwith liquids other than quench ing oils andthe invention is thereforenot to be construed as limited to any particular fluid to be treated.

In the tempering of steel, the steel at temperatures as high as 2000 1".is quenched in a bath of quenching oil which must be maintained near theproper temperature in order that the cooling of the steel, in tempering,be effected at acertain rate. The bath of quenching oil is heated by thebatches of steel being tempered and in order to maintain the propertemperature of the quenching oil, the quenching all must be continuouslyrecirculated through a cooler so as to maintain the desired temperatureof the quenching bath while tempering the steel. The quenching oil mayinclude a large percentage of lard oil which may deposit on the heattransfer surface of the c'ooler in the form of a wax. This wax builds upuntil the heat transfer between the cooling surface and the quenchingoil is greatly reduced and the capacity of the cooler greatlydiminished.

with oil cooling systems now in use, no adequate provision is made'fordewaxing the cooling \8.Claims. (01.257-2) close limits, that is, within1''. when used cool quenching oil.

Another object of the invention is to provide such apparatus which istullyautomatlc in maintalning the desired temperature of the liquidbeing treated.

Another object of the invention is to provide a simple and efl'ectlvecontrol for the minimum temperature of the liquid being treated by thesurface and also, with'systems now in use, while it is possible to coolthe quenching oilbath, no

provision is made for heating the bath. There;

'iore, at the start of theoperation of tempering steel, or in shiftingto higher temperature quenching. it has been the practice for theoperator to pass a few batches of hot steel through the bath merely tobring the bath up to the desired quenching temperature.

Thepassing of hot steel merely to. bring up the temperature ofadjustment of the character of the air supplied to the apparatus.

Another object of the invention s to provide such apparatus in whichsuch control can be effected entirely automatically in response to thetemperature oi the liquid being treated.

Another object is to provide such apparatus in which, where the coolingeifect is obtained from theevaporation of water. the amount of moistureevaporated to provide the cooling effect is reduced to a minimum.

Another object of the invention is to provide for dewaxlng the coolingsurface, when used for cooling quenching oil, so as to insure the properheat transfer between the cooling surface and the quenching oil at alltimes.

Another object 01' the invention is to provide for heating the quenchingoil. when desired, so as to bring it up to the proper temperaturefor-use' in tempering steel, and thereby avoid the I where the coolingeireet is obtained ironi the evaporation of water, a simple andeflective means for maintaining any desired minimum temperature of thespray water'whic'h is evaporated, thereby to provide a more exactcontrol the quenching bath to that desired involves, oi

course, waste labor and also. the possible loss of a large quantity ofsteel in the event that it cannot be retempered at the desiredtemperature.

It is one of the principal objects of the present invention to provide asimple and-efficient apparatus adapted to cool a fluid in which thecooling eflect is obtained from the evaporation of water, thereby togreatly reduce the amount of cooling operation of the apparat a w IAnother object of the invention is to provide such apparatus in whichthe temperature of the liquid beingtreated is maintained within veryOil.

of the cooling effect of the apparatus.

Another object is to maintain the apparatus under such conditions thatno substantial amounts; of lard oil are precipitated out on the coolingsurface, when used for cooling quenching --1 Other objects are toprovide such apparatus .which is simple and inexpensive in constructionand which will stand up under conditignhog severe and constant usewithout getting out of order or requiringrepairs.

In the accompanying drawing; Fig. 1 is a diagrammatic perspective viewof a heat exchanger embodying and carrying out the invention.

Fig. 2 is a fragmentary, vertical, transverse section, taken on line2-2, Fig. 1.

The heat exchanger shown, by way oi. example in the accompanyingdrawing, is particularly designed for maintaining the desiredtemperatureof thequenching oil used in tempering steel, in which use itoperates at most times to cool the quenching oil, provision being made,however, forheating the quenching oil and also to maintain the desiredminimum temperature of the water used for cooling, through the heatingmeans. The apparatus shown is designed to eflect cooling through theevaporation of water and includes a sheet metal casing which is mountedupon a tank 6 forming the base of the casing, this tank 6 containingabody of water I which is evaporated'to provide the cooling effect. .Thetank 6 is preferably extended beyond one end of the casing 5,

shown as provided with a top 3.

A plurality o1 fan housings ID are mounted in the upper part of thecasing 5, the, inlets of these fan housings being in communication withthe interior of the casing 5 so as to exhaust air therefrom. A commonshaft ll extends through the several fan housings l0. and is shown'asdriven by a motor I2 mounted on a bracket I 3 at one end of the casing5. Within each fan housing the shai't ll carries a fan l4 of anysuitable construcas indicated at 8, and this extension is.

quenching tank (not shown) a The quenching oil or other fluid to betreated is supplied through a tion, these fans drawing the air from theinterior I of the casing 5 and discharging it through the outlets I 5oi. the several tan housings which proiect upwardly through the top ofthe casing 5. These outlets discharge-the air into a vertical duct 20,the upper end of which forms an air discharge duct for exhausting theair to the outer atmosphere. A horizontal recirculation air duct 2|communicates with one side of the vertical duct- 20, this recirculationair duct discharging into a vertical duct 22' arrangedin rear of, thecasing 5 and this vertical duct 22 being provided with a lowerhorizontal leg 23 which is in communication with the lower part of thecasing 5 immediately above the tank 6. A cold air intake duct 26 alsodischarges into the vertical duct 22, this cold air intake duct beingpreferably in horizontal alinement with therecirculation air duct 2|.

..Means are provided for delivering difierent proportions ofcold'outside air from the duct 26 .andrecirculated or return air fromthe duct 2| intothe duct 22. For this purpose a fresh air damper 30 isarrangedin the cold outside air duct 26 and a recirculation damper 3| isarranged,

in the vertical air discharge duct 20 in position to close the openinginto the recirculation air duct 2|. This recirculation damper 3|, whenmoved away from the opening into the recirculation air duct, isalsomoved to restrict theair discharge duct 20 thereby to reduce theamount of air exhausted to the atmosphere in relation to the amount ofair recirculated through the recirculation duct 2|. I

The fresh air damper 30 is provided with an operating lever 32 whichprojects downwardly and the recirculation damper 3| isprovided with alever 33 which projects upwardly. The free ends of these levers 32 and33' are connected by a-bar 34, the central part of which isconnected bya link 35 with the arm 3601 a damper motor 31, this damper motor 31being shown as being line 42, the inlet and outlet lines 42, 43 ior'thequenching oil connecting with the headers of a.

bank of coils 44 arranged within the casing 5 im mediately above 'theopening from the duct 23. these coils being thereby arranged in the pathof the air drawn from the duct 23 and upwardly through the casing 5 bythe Ian wheels l4.

Immediately below the bank oi' coils 44 a second bank of coils 45 isarranged, this second bank of coils 45 being supplied with steam from asteam line 46, the condensate being withdrawn from these coils through aline 41. The steam or other heating medium supplied to the coils 45 isunder control of a valve 48 which is actuated in response to animmersion thermostat 43, the sensitive parts I of which are immersed inthe body of water 1 contained within the tank 8. The steam valve 48 canalso be placed under manual control and for' this purpose the immersionthermostat 49 is shown as connected to the steam valve 48 by a wire 50,and the other wires BI and 52 connected,-

respectively, with the steam valve 48 and immersion thermostat 49 areshown as connected through a manual switch 53 with the main power lines54 and 55. a

The water I to the tank 6 can be supplied in'any suitable manner and isshown as maintained at a constant level by an overflow connection 58inthe upper part of the tank 8, this overflow 56 leading to a drain line51 connected with the bot-' tom part or the tank 8. A drain valve 58 isprovided in thedrain line 51 between the tank 8 and the connectionof'this drain line 51 withthe overflow line Eli.

The water I in the tank 6 is withdrawn by a centrifugal spray water pumpill and is discharged through a vertical pipe 3| into a horizontal pipe62 extending lengthwise through the interior of the casing above thebank of coils 44. This pipe 62 carries a suitable number of branch pipes63, each of which carries a downwardlydischarging nozzle. The nozzles 64are arranged above the bank of coils 44 which carry the quenching oil orother liquid to be cooled so that these coils 44 are constantly flushedwith water. The excess water from the coils 44 falls back into the tank6 to be again recirculated bythe spray water pump 80.

Assuming that the quencbingoil is being used for tempering steel andthat the heat exchanger forming the subjectof the invention is operatinunder heavy cooling load conditions, th1s,.hot

mounted on a bracket 38 secured to theexterior of the duct 22. Thecontrol line 40 to the damper motor 31 connects with a thermostat 4|,the sensi- 'tive parts 01 which are immersed in the quenching oil orother fluid being cooled, which leaves the apparatus through a returnline 42, this return line discharging the quenching oil bath into thequenching oil enters the bank of cooling coils 44 from the supply line43 and is returned to the tempering bath through the line 42. Thequench- U lug oil so passing through the bank of coils 44 is arranged inthe stream of air which, under heavy cooling load conditions, is drawnby the fan wheels l4'i'rom the cold air intake duct 26 through thevertical duct 22 and horizontal leg 23 into the bottom of the casing 5,this cold outside air being.

drawn vertically upward through the casing-5 and discharged by the fanwheels l4 into the air discharge duct 20. At the same time the body ofwater 1 in the tank 6 is, being pumped by the spray water ump 60,through the'pipes 6 l, 62 and 63 and is sprayed onto the bank of coils44 by the nozzles 64, the excess spray water collecting in the tank 6.-The'bank of coils 44 carrying the hot quenching oil is'threby floodedwith water. this water evaporating on these coils, the coils 44 tendingto assume the wet bulb temperature of the air drawn upwardly throughthese coils by the fan wheels I4. The quenching oil passing througheases pered batch of steel and the introduction of a batch of hot steelinto the bath of quenchin! oil to be tempered, the falling temperatureof the quenching oil leaving the apparatus through the quenching oilreturn line 42 actuates the thermostat 4| and the damper motor llconnected to this thermostat through the control line .40 to move thefresh air damper lli toward its closed position and the recirculationdamper II toward its open position. When this occurs recirculation airfrom the air discharge duct 20 is drawn, together with thefresh air fromthe cold air irtake duct 26, through the vertical duct 22 and itshorizontal leg 23 into the bottom of the casing 5. Since thisrecirculation air withdrawn from the air discharge duct 20 has beenheated by passing the bank of coils 44 and also is substantiallysaturated with the moisture evap orated in passing through these floodedcoils 44 and thesprays from the nozzles 64, it will be seen that themixed fresh and recirculated air now supplied to the bottom of thecasing has a higher wet bulb temperature and hence the evaporativecooling effect of the water and air passing over the bank of coils 44 isreduced. It will therefore be seen that the immersionthere mostat 4|maintains a constant minimum temperature of the quenching oil returnedto the quenching bath by the inverse operationof the recirculationdamper 3| and fresh air damper 30, a falling temperature of thequenching oil or other liquid being treated opening the recirculationdamperll and closing the cold fresh air damper 30. This modulatingcontrol of the dampers 30 and 3| allows the intermediate positionofthese dampers to hold a constant minimum temperature of the quenchingoilby the use of recirculated air and tempered cold fresh air.

The recirculation of the necessary amount of airfrom the air dischargeduct 20 to the bottom of the casing 5 in so maintaining a' constantminimum temperature of the quenching oil or other liquid being treatedalso keeps the amount of evaporated'moisture to a minimum. The ar--rangement of the recirculation damper 3| in the air discharge duct 20also serves to reduce the amount of air exhausted through the outlet ofthe discharge duct 20 with an increase in the amount of recirculated airreturned to the bottom of the casing 5.

The primary purpose of the immersion ther mostat it in the spray watertank 8 is to keep the water temperature above a predetermined In theevent that the temperature of the quenching oil drops below thatrequired for properly tempering the steel, as at the start of operationor in an extended period between tempering operations, the immersionthermostat 4! is actuated by the lowering temperature of the water I inthe tank} to open the steam valve 48 and admit steam to the steam coils45. This thermostat 49 serves to maintain a constant min- 1 Under imumtemperature of the spray water. these conditions, the immersionthermostat 4| has moved the fresh air damper 30 to its fully closedposition and the recirculation damper ii to its fully opened positionand hence the air heated by the steam coils is continuously recirculatedby the fan wheels l4, through the air discharge duct 20, recirculationduct 2|. vertical duct 22, and horizontal leg 23 to the bottom of thecasing 5, this air moving upwardly through the bank of coils 44 carryingthe quenching oil or other liquid being treated so as to heat the same.Since this recirculating air is. saturated with moisture, there is noevaporative cooling effect and hence the quenching oil passing throughthe bank of coils 44 is heated so as to keep the bath of quenching oilat the desired minimum temperature under all conditions of operation.

If the cooling coils 44 which carry the quenching oil become waxed upinternally due to the deposit of lard oil in the form of a wax therein,

the heat exchanger can be manually adjusted to operate'in the same wayas when the quenching oil is below the set temperature as Justdescribed. Thus, to dewax the cooling coil 44,

the fresh air damper ill is held closed, the recirculated air damper isheld open and steam, under control of the manual switch 53, is admittedto the steam coil 45. The air being recirculated through the casing 5 isthereby heated so as to melt the wax in the cooling coils 44, this waxbeing carried away with the quenching ofl.

While the invention has been described particularly in conjunction withthe cooling of quenching oils, it will be understood that it is notlimited to this particular use but may be used in conjunction with anyfluid to be treated as indicated in the accompanying claims. While theinvention has also been illustrated as embodied in an evaporative typeof heat exchanger, the use of the spray water for evaporative cool ingis not an essential feature of the invention in its broader aspect.

minimum. With quenching oils, this minimum is in the range of 50 to F.,and by keeping the spray water at this minimum temperature, the minimumamount of lard oil will be deposited out in the cooling coils 44. Bysetting the ther- .mostat 49 to maintain, through the'steam coils 45,this minimum temperature of the spray water, the deposit of wax in thecoils 44 is reduced toa minimum since it has been ascertained that attemperatures above 55 F. practically no lard oil will deposit out ofquenching oils. Other means could, of course, be provided for somaintaining the minimum temperature of the spray water and themaintenance of this minimum temperature could, of course, be maderesponsive to the leaving temperature of the quenching oil, as throughthe thermostat 4 i I It will be-seen, so far as the control of theproportions of fresh and recirculated air ad- 'mitted to the casing 5 isconcerned, that an important feature ofthe invention resides in thiscontrol being responsive to' the temperature of the liquid being cooled.It will also be apparent that this control can be accomplished directly,as by the immersion thermostat shown, or indirectly, as by response to atemperature which varies in substantial proportion to the temperature ofthe liquid being cooled. The claims are therefore not to be construed asspecifically limited to the use of the immersion thermostat 4| but asincluding control means which are indirectly responsive to thetemperature of the quenching oil or other liquid being cooed.

From the foregoing it will be seen that the present invention provides asimple and emcient apparatus for maintaining the desired temperature ofa fluid within very close limits; which has a high cooling capacity witha minimum consumption of cooling water, and which will prevent theliquid beingv treated from droppingbelow the desired minimumtemperature. Further, when the cooling surfaces become waxed up due tothe deposit of any material, such as lard oil, on the cooling surface,this surface can quickly and easily be dewaxed.

We claim as our invention; g 1.. A heat exchange device for cooling astream of fluid, comprising means forming a chamber having an air inletat one end and an air outlet at its opposite end, a fan arranged toforce a stream of air from saidinlet, through said chainher and outthrough said outlet, a cooling coil arranged in the stream of airpassing through said chamber, means for discharging and distributingwater over said cooling coil to wetthe exterior of a part ofthe streamofair leaving said chamber back to said air'inlet, and means foradjusting the'relative amounts of outside. and recirculated said coolingcoil and to evaporate and absorb heat therefrom, means for continuouslyconduct-' ing the said stream of fluid to be cooled through said coolingcoil, a duct for conducting-outside air to said air. inlet, arecirculation duct conducting a part of the stream of air leaving saidchamber back to said air inlet and means for adjusting the relativeamounts of outside and recirculated air admitted to said air inlet tomaintain a minimum surface temperature of said cooling coil comprisingdamper means in the currents of outside and recirculated air passingthrough said outside air and recirculated air ducts and movable torestrict'the flow of one of said currents of air and to relieve therestriction to the flow of the other of said currents of air and viceversa and .a thermostat responsive to the temperature ofsaid stream offluid and regulating said dampers.

2. A heat exchange device for cooling a stream of fluid, comprisingmeans forming a chamber having an air inlet and an air outlet, a fanarranged to force a stream of air from said inlet, through said chamberand out through said outlet, a cooling coil arranged in the stream ofair passing through said chamber, means fordischarging and distributingwater over said cooling coil to wet the exterior of said cooling' yiland to evaporat and absorb heat therefrom, means for continuouslyconducting the said stream of fluid to be cooled through said coolingcoil, means for conducting outside air to said air inlet, recirculationmeans for conducting a part of the stream of air leaving said chamberback to said air inlet and thermostat means responsive to thetemperature of said stream of fluid and adjusting the amount of air soconducted back by said re-- circulation means to maintain a minimumsurface temperature of said cooling coil.

3. A heat exchange device for maintaining a fluid in a selectedtemperature range determined by the character of the fluid by cooling astream of said fluid and preventing the temperature ,thereof fromfalling below said temperature range, comprising means forming a chamberhaving an air inlet at one end connecting with the outside air and anair outlet at its opposite end, a fan arranged to force a stream of airfrom said inlet, through said chamber and out through said outlet, acooling coil arranged in the stream of air passing through said chamber,

means for discharging and distributing a stream air admitted to said airinlet to: prevent the tem-v peratureof said fluid in said cooling coilfrom falling below said temperature range, comprising damper means inthe currents of outside and re-' circulated air passingthrough saidoutside and recirculated air ducts and movable to restrict the flow ofone of said currents of air and torelieve the restriction to the flow ofthe other of said currents of air and vice versa and thermostat meansresponsive to the temperature atom of said streams and regulating saiddampers. v

4. A heat exchange device for maintaining a fluid in a selectedtemperature range determined by the character of the fluid by cooling astream of said fluid and preventing the temperature thereof from fallingbelow said temperature range, comprising means forming. a chamber havingan air inlet and an air outlet, a fan arranged to force a stream of airfrom said inlet, through said chamber and out through said outlet, acooling coil arranged in the stream of air passing through said chamber,means fortherefrom; means for continuously conducting part of the streamof air leaving said chamber back to said air inlet, and thermostat means'responsive to the temperature of one of said streams to adjust theamount of air so conducted back by said"recirculation means to preventthe temperature of said fluid in said cooling coil from. falling belowsaid temperature range.

5. A heat exchange device for cooling a stream or fluid, comprisingmeans forming achamber having an air inlet-at one end and an air outletat its opposite end, a fan arranged to force a stream of air from saidinlet, through said chamher and out through said outlet, a cooling coilarranged in the stream of air passing through said chamber, means forcontinuously conducting the said stream of fluid to be cooled throughsaid cooling coil, a duct for conducting outside air to said air inlet,a recirculation duct conducting a part of the stream of air leaving saidchamber back to said air inlet and means for adjusting the relativeamounts of outside and recirculated air admitted to said air inlet tomaintain a minimum surface temperature of said cooling coil comprisingdamper means in the currents of outside and recirculated air passingthrough said outside air and recirculated air ducts and movabletorestrict the flow of one of said currents of air and to relieve therestriction to the flow ofthe other of said currents of air and viceversa and a thermostat responsive to the temperature of "said stream offluid and regulating -said,

dampers.

6. A heat exchange device for cooling a stream of fluid, comprisingmeans forming a chamber back to said air a 22,583 Y i be cooled throughsaid cooling coil, means for conducting outside air to said air inlet,recirculation means for conducting a part of the stream of air leavingsaid chamber'back to said air inlet and thermostat means responsive tothe temperature of said stream of fluid and adjusting the amount of airso conducted back by said recirculation means to maintain a minimumsurface temperature of said cooling coil.

' '7. A heat exchange device for maintaining a uid in a selectedtemperature range determined I y the character of the fluid by cooling astream at said fluid and preventing the temperature thereiif fromfalling below said temperature range, comprising means forming a chamberhaving an air inlet at one end connecting with the outside air and anair outlet at its opposite end, a an arranged to force a stream of airfrom said inlet, through said chamber and out through said outlet, acooling coil arranged in the stream of air passing through said chamber,means for continuously conducting the said stream of fluid to be cooledthrough said cooling coil said stream of air normally being heatedthrough heat derived from said stream of fluid passing through saidcooling coil, a recirculation duct conducting a part of the stream ofair leaving said chamber the? relative amounts of outside andrecirculated -air,admitted to said air inlet to prevent the tem-.

pefialture' of said fluid in said cooling coil from i'alling below saidtemperature range, comprising damper means inthe currents of outside andrecirculated air passing through said outside and recirculated air ductsand movable to restrict the flow of one of said currents of air and torelieve the restriction to the flow of the other or said currents of airand vice versanand thermostat means responsive to the temperature of oneof said streams and regulating said damper.

8. A heat exchange device for maintaining a fluid in a selectedtemperature range determined by the character of the fluid by cooling astream of said fluid and preventing the temperature inlet, and means foradjusting thereof from falling below said temperature range, comprisingmeans forming a chamber having an air inlet and an air outlet, a fanarranged to force a stream of air from said inlet, through said chamberandout through said outlet, a cooling coil arranged in the stream of airpassing through said chamber, means for continuously conducting the saidstream of fluid to be cooled through said cooling coil, said stream ofair normally being heated through heat derived from said stream of fluidpassing through said cooling coil, means forconducting outside air tosaid air inlet, recirculation means for conducting apart of the streamof air leaving said chamber back to said air inlet, and thermostat meansresponsive to the temperature of one of said streams to adjust theamount of air so conducted back by said recirculation means to preventthe temperature of said fluid in said cooling coil from falling belowsaid temperature range.

- MARTIN H. OLSTAD.

